1. Field of the Invention
This invention relates to electrical switching apparatus and, more particularly, to circuit breakers having one or more pairs of separable contacts.
2. Background Information
Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. In small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typically provided by a thermal-magnetic trip device. This trip device includes a bimetal, which heats and bends in response to a persistent overcurrent condition. The bimetal, in turn, unlatches a spring powered operating mechanism, which opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system.
xe2x80x9cSlow makexe2x80x9d is defined as the closing velocity of the circuit breaker separable contacts being directly dependent upon the closing speed of the operating handle. For a circuit breaker operating at relatively high voltages (e.g., 480 to 600 VAC), this results in a greater tendency for the separable contacts to weld closed, and significantly reduces the number of switching operations in the operating life of the circuit breaker.
There is room for improvement in circuit breakers.
The present invention is directed to a circuit breaker in which a first end of an operating mechanism pivot lever blocks movement of a movable contact arm when a surface of an operating handle blocks the other end of the pivot lever, and in which the first end of the pivot lever releases the movable contact arm when the surface of the operating handle releases the other end of the pivot lever as the operating handle is moved to an intermediate position thereof. In turn, the movable contact arm and its movable contact rapidly rotate toward a fixed contact in response to the bias of an operating mechanism spring.
An accordance with the invention, a circuit breaker comprises: a housing; a fixed contact; an operating mechanism including a movable contact arm pivotally mounted thereto and a spring, the movable contact arm having a movable contact adapted for engagement with the fixed contact, the spring biasing the movable contact arm and the movable contact toward the fixed contact; an operating handle having an OFF position, an ON position, and an intermediate position between the OFF and ON positions, the operating handle including a handle member having an extension; a blocking member having a bias member, a first surface, a second surface and a third surface, the handle member and the blocking member being co-pivotally mounted to the housing, the extension of the handle member engaging the third surface of the blocking member for rotation therewith; a pivot lever including a first end adapted for engagement with the movable contact arm, and including a second end adapted for engagement with the first and second surfaces of the blocking member, the first surface of the blocking member blocking the second end of the pivot lever as the operating handle is moved from the OFF position toward the intermediate position thereof, and the first surface of the blocking member releasing the second end of the pivot lever to the second surface of the blocking member as the operating handle is moved to the intermediate position thereof, wherein the first end of the pivot lever blocks movement of the movable contact arm when the first surface of the blocking member blocks the second end of the pivot lever, and wherein the first end of the pivot lever releases the movable contact arm when the first surface of the blocking member releases the second end of the pivot lever as the operating handle is moved to the intermediate position thereof, thereby moving the movable contact arm and the movable contact toward the fixed contact in response to the bias of the spring.
When the fixed and movable contacts are welded closed, the second end of the pivot lever may engage the extension of the operating handle and limit rotation of the operating handle from the intermediate position to the OFF position.
The blocking member may be a blocking disk. The first surface may be a first diameter of the blocking disk, the second surface may be a second diameter of the blocking disk, and the third surface may be between the first and second surfaces. As the operating handle is moved from the OFF position toward the intermediate position thereof, the extension of the handle member may engage the third surface of the blocking disk for movement therewith. The first end of the pivot lever may release the movable contact arm when the first diameter of the blocking disk releases the second end of the pivot lever to the second diameter of the blocking disk as the operating handle is moved to the intermediate position thereof.
The pivot lever may include a first arm having the first end and a second arm having the second end. As the operating handle is moved from the ON position toward the intermediate position thereof, the extension of the handle member may engage the second arm of the pivot lever and pivot the first arm and the first end of the pivot lever to engage the movable contact arm for movement of the movable contact thereof away from the fixed contact.